Machines have been developed for preparing beverages, such as, for example, coffee-making machines, which have the special characteristic that the pressure of liquid to obtain the coffee is procured using systems alternative to the electric pressure pump. The intention is to obtain autonomous machines, wherein the coffee can be made without electric pumps and the problems of maintenance and low energy efficiency entailed by the use of water heating systems based on serpentines or heat exchangers associated with said electric pumps.
International patent application WO2010/113116 discloses a machine for preparing coffee of the type mentioned, comprising an infusion chamber for housing a dose of product and a hydraulic accumulator device configured by a distribution cylinder and piston assembly which is disposed adjacently disposed on said infusion chamber and is susceptible of storing, in an active position, potential energy from the compression force applied to a spring or fluid associated with the rod of said piston.
In the machine of said patent application, the potential energy accumulated by the piston can be transmitted in the form of pressure to the water of the chamber, when said piston comes into contact, in its active position, with the water of said chamber. To retract the piston to its active position, the same application discloses a system of axial traction that enables the traction of the rod of said piston exerting a relatively small force on a lever to overcome the opposition of the fluid or spring. The retraction of this same piston makes it possible to load the water from a reservoir by suction due to decompression whilst the passage valve of the machine's distribution conduit remains closed.
The machine disclosed in said patent has the advantage that it enables the continuous and stable distribution of liquid at a constant high pressure of 6 to 10 bar (pressure necessary for espresso coffee), optimising the power consumption and the manufacturing and maintenance costs of the machines for preparing beverages of the state of the art. Furthermore, the machine disclosed in said application has the advantage of being very small and compact, for which reason it can easily be transported from one place to another, in the workplace or, for example, open air activities.
Another advantage of this machine lies in the fact that it requires little maintenance, since it has conduits of very short length which substantially reduce the calcification problems present in other machines of the state of the art.
However, it has been observed that the machine described in said state of the art has a drawback. For example, it has been detected that its size is still excessive for portable use. Furthermore, it has also been observed that the number of components is still too high, which negatively affects its manufacturing cost.